Sullivan ran as the most qualified of the group to defeat Begich. His nomination has been the expected outcome for months, but the general-election race couldn’t start in earnest until Sullivan dispensed with his Republican foes.

Sullivan led with 40 percent of the vote when The Associated Press called the race early Wednesday morning with 80 percent of precincts reporting. He was followed by 2010 Senate nominee Joe Miller with 32 percent, Lt. Gov. Mead Treadwell with 25 percent and a fourth candidate, John Jaramillo, with 3 percent.

Sullivan, an Ohio-born attorney, is a lieutenant colonel in the Marine Corps Reserves and was an assistant secretary of State in the George W. Bush administration. He resigned his natural resources post a year ago to run for office, and now he’s emerging from a late primary to take on an incumbent lauded by operatives in both parties as a skilled politician.

In a midterm cycle and in a state President Barack Obama lost by 14 points two years ago, the race is rated Tilts Democratic by The Rothenberg Political Report/Roll Call.

Despite having to wait until now for an official GOP nominee, the Begich campaign isn’t starting from scratch. The senator and a pro-Begich super PAC spent big on TV to both define the incumbent and his most likely opponent.

Begich has sought to paint himself as a tireless advocate of Alaska values, even when that runs contrary to Obama’s agenda. The crux of the Democrats’ argument against the Republican is that Alaskans can’t trust Sullivan, whose roots in the state go back less than 20 years.

The Harvard grad, who turns 50 in November, met his wife while a student at Georgetown Law School. After serving in the Marine Corps, Sullivan moved to her home state of Alaska in 1997. While a member of the Marine Corps Reserves, Sullivan served as a law clerk on the 9th Circuit Court of Appeals, then clerked for a state Supreme Court justice before joining Perkins Coie.

Sullivan left the state in 2001 for a fellowship on the staff of National Security Adviser Condoleezza Rice. He was recalled to active duty for an 18-month stint in late 2004, then was confirmed by the Senate in May 2006 to serve at State.

He returned to Alaska in early 2009 and was appointed state attorney general by then-Gov. Sarah Palin. A year later, Palin’s successor appointed him to the natural resources post.

Running for office for the first time, Sullivan had the support in the primary of more than a dozen senators of all GOP stripes, plus outside groups such as the Club for Growth and American Crossroads. He raised $4 million, far outpacing his GOP colleagues. But he had just under $1 million in cash on hand as of July 30 — half of Begich’s war chest.

Still, money is unlikely to be a determining factor in this race. Outside groups and both national party committees have reserved millions of dollars worth of time on the state’s cheap airwaves.